Method of forming characters for microprint and image forming apparatus using the same

ABSTRACT

Disclosed is a method of forming characters for microprint and an image forming apparatus using the same. The method of forming characters for microprint includes determining for every image character a size font taking into account the rules to create small prints, rasterizing a character into a bitmap, skeletonizing the bitmap, reformatting the bitmap maintaining a character legibility, storing the bitmap, and forming halftoning cells from the reformatted bitmap.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of prior application Ser.No. 12/356,700, filed on Jan. 21, 2009, in the United States Patent andTrademark Office, which claims priority from Russian Patent ApplicationNo. 2008101807, filed on Jan. 23, 2008 in Russian Agency for Patents andTrademarks, and Korean Patent Application No. 10-2008-0116797, filed onNov. 24, 2008 in the Korean Intellectual Property Office, thedisclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present general inventive concept relates to the methods of formingcharacters for microprint and related technologies and an image formingapparatus using the same, and more particularly, to methods of formingcharacters for microprint and related technologies and an image formingapparatus using the same, which could be used in modern color andblack-and-white printers and multifunction printing devices, thuseliminating the necessity to employ g special micro-fonts.

2. Description of the Related Art

Microprint serves as a function or method to protect and prevent againstforgery and unauthorized copying, since it is very difficult to copy atext of very small size correctly in attempt to counterfeit a bank-noteor other document bearing a microprinted or related text imprintedthereon. When a bank-note or other document is put into a photocopier,computer scanner, or related device, a line with a microprint text willbe perceived by the copier or scanner as a dashed line that will bethereafter rendered as a counterfeit bank-note or printed document.Thus, forgery and unauthorized copying can be prevented. When copied,the microprint will also not be rendered verbatim and literatim inattempts of forgery and unauthorized copying using an offset printingmachine, since the text is too small for engraving with lithographicplates using methods well-known for general public or counterfeiters.Therefore, microprint used together with other methods to protect fromforgery of bank-notes and documents serves generally for confirmation ofthe fact of authenticity of a printed bank-note or document.

Moreover, employment of microprint is widespread in producing documentsprotected from copying. Examples of solutions involving microprinttechnology can be found, e.g., in U.S. Pat. Nos. 5,823,576, 6,045,656,7,152,047, and 7,270,918.

Professional offset devices are used in microprinting technology. It isoften impossible to print a readable text with a font of a very smallsize in one typographical point and less possible by employing a normalfont and user printing devices. Characters printed with a small sizesuch as one typographical point are significantly distorted andsubstantially illegible.

Special micro-fonts are usually employed in microprinting. However,every micro-font includes a limited set of characters, e.g., for severallanguages only, and it is impossible in general to print an arbitrarycharacter. An additional memory is required to store micro-fonts.Development of micro-fonts is a long and complex autonomous process.

Related art to the present general inventive concept are the method andsystem to print microtext disclosed in the US Patent Laid-outApplication No. 2007/0252838, which provide a special micro-font basedon the PostScript Type 3 font. This related art has the followingdisadvantages: the special micro-font is developed autonomously, whichdeteriorates the usability and requires an additional memory to storethe developed micro-font. The micro-font has a limited set ofcharacters, which narrows the range of use thereof. Additionally,special printing devices having a capability of high resolution printare required to microprint, which also narrows the range of use of therelated art method and usability thereof.

SUMMARY OF THE INVENTION

An aspect of the present general inventive concept is to provide amethod to form micro-font characters having an enlarged range of use andenhanced usability with reduced volume of the used memory, and an imageforming apparatus using the same.

Additional aspects and utilities of the present general inventiveconcept will be set forth in part in the description which follows and,in part, will be obvious from the description, or may be learned bypractice of the general inventive concept.

There may be provided a method of forming characters for microprint, themethod including determining for every image character, a size of afont, rasterizing a character into a bitmap, skeletonizing the bitmap,reformatting the bitmap maintaining a character legibility, and forminghalftoning cells from the reformatted bitmap.

Skeletonizing the bitmap may be performed by a parallel thinning.

Reformatting the bitmap may include determining a pixel significance,and selecting and deleting, at each stage of a multiple iterationreduction, at least one combined group of less significant pixels in thevertical or horizontal direction.

The selecting and deleting of the group of less significant pixels maysolve a problem of finding a graph path by applying a dynamicprogramming algorithm that minimizes a cumulative cost of the trajectoryusing a graph at a regular network according to the cost map.

A pixel significance may be determined using a weighted cost function,wherein the white pixels of the background have a least cost, terminalor branch pixels of the skeleton have a high or a highest cost dependingon the distance to each of them from a reference point, and other pixelsof the skeleton of the image character have medium cost depending on thedistance to the nearest one of the terminal or branch pixels.

The halftoning cell may be formed from one or several reformattedbitmaps.

The halftoning cell may be formed from a fragment of the reformattedbitmap.

An embodiment of the present general inventive concept may be achievedby providing an image processing unit to form characters for microprintby rasterizing a character into a bitmap skeletonizing the bitmap,reformatting the bitmap maintaining a character legibility, and forminghalftoning cells from the reformatted bitmap and a printing unit toprint the characters for microprint on a print medium.

The image processing unit may perform a parallel thinning to skeletonizethe bitmap.

The image processing unit may reformat the bitmap by determining a pixelsignificance, and selecting and deleting, at each stage of a multiplereduction, at least one combined group of less significant pixels in thevertical or horizontal direction.

The image processing unit may solve a problem of finding a graph path byapplying a dynamic programming algorithm that minimizes a cumulativecost of the trajectory using a graph at a regular network according tothe cost map.

The image processing unit may determine the pixel significance using acost function, wherein white pixels of the background have a least cost,terminal or branch pixels of the skeleton have a high or a highest costdepending on the distance to each of them from a reference point, andother pixels of the skeleton of the image character have medium costdepending on the distance to the nearest one of the terminal or branchpixels.

The image processing unit may form the halftoning cell from one orseveral reformatted bitmaps.

The image processing unit may form the halftoning cell from a fragmentof the reformatted bitmap.

Exemplary embodiments of the present general inventive concept may alsobe achieved by providing a method for forming characters for microprint,the method including performing a multiple iterative reduction of abitmap, and determining at the stages of the multiple iterativereduction a pixel significance and deleting pixels having a smallsignificance. At least one combined group of characters is deleted toobtain a new copy of the bitmap having a changed size.

Exemplary embodiments of the present general inventive concept may alsobe achieved by providing a method for forming characters for microprint,the method including deriving an initial size of a print font of a textfragment, and performing a microprinting operation when the initial fontsize is less than or equal to one typographical point.

Exemplary embodiments of the present general inventive concept may alsobe achieved by providing a method for forming characters for microprint,the method including checking whether an existing bitmap of a microtextcharacter is stored for the microtext character, and generating a newbitmap and halftoning cell of the microtext character when there is notan existing bitmap.

Exemplary embodiments of the present general inventive concept may alsobe achieved by providing a computer readable medium to containcomputer-readable codes as a program to perform a method, the methodincluding determining for every image character, a size of a font,rasterizing a character into a bitmap, skeletonizing the bitmap tocreate a skeleton, reformatting the bitmap maintaining a characterlegibility, and forming halftoning cells from the reformatted bitmap.

The technical result of the present general inventive concept consistsin enlarging the range of use, enhancing the usability and reducing thememory volume required for carrying out the method.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and utilities of the present generalinventive concept will become apparent and more readily appreciated fromthe following description of the embodiments, taken in conjunction withthe accompanying drawings of which:

FIG. 1 illustrates an operational diagram of carrying out the method toform characters for the microprint in accordance with the presentgeneral inventive concept

FIG. 2 illustrates the example of processing two characters using themethod to form characters for the microprint in accordance with thegeneral inventive concept.

FIG. 3 illustrates the example of plotting the trajectories to deleteone vertical and one horizontal lines.

FIG. 4 illustrates the example of the script in the PostScript languageto print a microtext character forming a halftoning cell.

FIG. 5 illustrates an operational diagram of the method to microprintusing the method to form characters for the microprint in accordancewith an exemplary embodiment of the present general inventive concept.

FIG. 6 illustrates a schematic block diagram of an image formingapparatus in accordance with an exemplary embodiment of the presentgeneral inventive concept.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order to better understand the general inventive concept generalinventive concept, the detailed description along with the accompanyingdrawings is adduced below.

Reference will now be made in detail to the embodiments of the presentgeneral inventive concept, examples of which are illustrated in theaccompanying drawings, wherein like reference numerals refer to the likeelements throughout. The embodiments are described below in order toexplain the present general inventive concept by referring to thefigures.

An operation to implement a method to form characters for microprintusing the example of two image characters is considered with referenceto FIGS. 1 and 2. In an operation designated as (S101), a suitable fontsize taking into account the rules for forming small prints is selected.While selecting the font, a compromise between the bitmap size andcharacter legibility is complied with. In an operation designated as(S102), a character rasterization into the bitmap, i.e., into an imageof FIGS. 2( a) and 2(d) is preformed by applying the selected font size.The character is always rasterized as black pixels in the foreground ofa white background or white pixels in the foreground of a blackbackground, without taking into account the color of the initialcharacter and background.

In an operation designated as (S103), the bitmap is skeletonized,herewith employing preferably, from the variety of existingskeletonization algorithms (thinning, constructing a carcass), one oftechnologies of parallel thinning described in the article by LouisaLam, Seong-Whan Lee, and Ching Y. Suen, “Thinning Methodologies—AComprehensive Survey”, IEEE Tr. PAMI, vol. 14, no. 9, pp. 869-885,1992). The result of the bitmap skeletonization is illustrated in FIGS.2( b) and 2(e).

In an operation designated as (S104), the bitmap is reformattedmaintaining a character legibility, herewith performing a multipleiterative reduction of the bitmap, and determining, at the stages of themultiple iterative reduction, a pixel significance and deleting pixelshaving a small significance. In order to prevent a distortionoccurrence, at least one combined group of less significant pixels inthe vertical or horizontal direction is determined at every stage of themultiple iterative reduction. The essence of the operation designated as(S104) consists in repetition and deleting herewith, at every reducingoperation, at least one combined group of characters to obtain a newcopy of the bitmap having a changed size. The obtained bitmap is used asthe initial one for the next iteration, and the process is repeateduntil obtaining a required size. The pixel significance is determined bya weighted cost function, in which the pixels of the white backgroundhave the least cost, terminal or branch pixels of the carcass orskeleton of an image fragment have a high or the highest cost dependingon the distance to each of them from a reference point, and other pixelsof the carcass or skeleton have a medium cost depending on the distanceto the nearest one of the terminal or branch pixels.

Owing to pixel deletion, the distances from a reference point, and hencethe pixel costs may be changed through multiple iterations. A cost mapis calculated, where every element of the carcass or skeleton representsa significant pixel in the bitmap. The cost map is used to assign aweight for graph arcs of the carcass or skeleton that are directedtowards an element of the cost map. In order to solve a problem offinding an optimal path of junctions in the vertical or horizontaldirection, a graph is plotted at a regular network according to the costmap. The optimal path is determined as a trajectory having a minimalcumulative cost. This trajectory can be found using a dynamicprogramming algorithm (one of the suitable algorithms is described inthe article by Shai Avidan, Ariel Shamir, “Seam Carving forContent-Aware Image Resizing”, ACM Transactions on Graphics, Volume 26,November 3, SIGGRAPH 2007). FIGS. 2(c) and 2(f) show the outputreformatted image characters for a bitmap of 10×10 pixels.

FIG. 3 illustrates an example of assigning pixel cost and plottingtrajectories to delete one vertical and one horizontal line: FIG. 3 (a)demonstrates values of the pixel weights in the beginning of theiteration, all pixels of the white background having the least cost.FIG. 3( b) illustrates a found trajectory in the vertical direction, ofwhich the trajectory has a minimal cumulative cost. FIG. 3( c)illustrates a result of this iteration, i.e., reformatting the bitmap byway of deleting the pixels of the found trajectory. FIG. 3 (views FIGS.3( d), 3(e) and 3(f)) demonstrate the next iteration that consists infinding and deleting a pixel trajectory in the horizontal direction.

In an operation designated as (S105) illustrated in FIG. 1, generationof a halftoning cell from the reformatted bitmap is performed. In thisoperation, there is a possibility to take into account a charactercolor. FIG. 4 illustrates a fragment of the script in the PostScriptlanguage to print a microtext character by forming the halftoning cell.

The method to form characters for microprint according to an exemplaryembodiment of the present general inventive concept could be applied forseveral print protocols and languages. Moreover, there is a possibilityto include the bitmaps of several characters into one halftoning cell,and, conversely, only a fragment of the character bitmap could beincluded into one halftoning cell.

FIG. 5 illustrates an exemplary operational diagram of a method tomicroprint using a method to form characters for microprint. In anoperation designated as S501, the initial size of the print font of thecurrent text fragment is derived. If the initial font size is less thanor equal to one typographical point, then the font size relates to themicrotext (condition S502), and the operations of microprinting areperformed. The condition (S503) checks, whether an existing bitmap ofthe microtext character was stored for this character. If this characteris processed for the first time, then the character for microprinting isformed, that is, a new bitmap of the microtext character and halftoningcell are generated in an operation designated as (S504). The microprintof the current character is performed in an operation designated as(S505). Further, a subsequent processing of the current text fragment isperformed in an operation designated as (S506).

The method to form characters for microprint according to an exemplaryembodiment of the present general inventive concept is based on thefollowing image conversion technologies: rasterization into sufficientlylarge bitmap, skeletonization, and specific reformatting of the bitmapmaintaining the legibility.

The real time conversion rate in the method depends on the bitmap sizethat depends in turn on the font size and print resolution. Preferably,the font size for rasterization is selected of 5 to 8 typographicalpoints.

The method to form characters for microprint according to an exemplaryembodiment of the present general inventive concept permits anadditional possibility of microprinting to the modern color andblack-and-white printers and multifunction printing devices withoutemploying special micro-fonts. Characters of any fonts could beconverted into microtext in real time. It is possible to build theproposed method into a raster image processor (RIP) or printer driver.

FIG. 6 is a schematic block diagram of an image forming apparatus inaccordance with an exemplary embodiment of the present general inventiveconcept. Referring to FIG. 6, an image forming apparatus 600 includes animage processing unit 610 to process image characters, and a printingunit 620 to print the processed image characters on a print medium. Inthis exemplary embodiment, the image forming apparatus includes aprinter, a multifunction peripheral (MFP), a digital copying machine, orother known image forming device. The image forming apparatus of thepresent general inventive concept also includes a memory unit 640. Thememory unit 640 may further include non-volatile memory such as a ROMunit to store program data to carry out the algorithms as describedherein as well as volatile memory such as a RAM unit to temporarilystore image and other data received from the host 630, other inputsources, or data generated during any of the processes described herein.

The image processing unit 610 forms characters for microprint based onthe image characters of a suitable font size taking into account therules for forming small prints provided from a host 630. That is, thecharacters for microprint are formed by rasterizing the image characterinto a bitmap, skeletonizing the bitmap, reformatting the bitmapmaintaining a character legibility, and forming halftoning cells fromthe reformatted bitmap. The image processing unit 610 processes theimage on the basis of the foregoing method of forming characters formicroprint according to an exemplary embodiment of the present generalinventive concept, and thus repetitive descriptions thereof will beavoided.

The printing unit 620 prints the characters for microprint formed by theimage processing unit 610 on a print medium. The printing unit 620 formsan image by an inkjet method, a thermal transfer method, anelectrophotographic method, or other known methods or processes. Theconfiguration and the image forming mechanism of the printing unit 620are publicly known, and therefore descriptions thereof will be omitted.

The present general inventive concept can also be embodied ascomputer-readable codes on a computer-readable medium. Thecomputer-readable medium can include a computer-readable recordingmedium and a computer-readable transmission medium. Thecomputer-readable recording medium is any data storage device that canstore data as a program which can be thereafter read by a computersystem. Examples of the computer-readable recording medium includeread-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetictapes, floppy disks, and optical data storage devices. Thecomputer-readable recording medium can also be distributed over networkcoupled computer systems so that the computer-readable code is storedand executed in a distributed fashion. The computer-readabletransmission medium can transmit carrier waves or signals (e.g., wiredor wireless data transmission through the Internet). Also, functionalprograms, codes, and code segments to accomplish the present generalinventive concept can be easily construed by programmers skilled in theart to which the present general inventive concept pertains.

Further, the method of forming characters for microprint according to anexemplary embodiment of the present general inventive concept may beachieved by a printer driver installed in the host. Also, someoperations of this character forming method may be implemented by theprinter driver, and the other operations may be implemented by the imageprocessing unit of the image forming apparatus.

While the above embodiment of the present general inventive concept hasbeen set forth as illustrating the present general inventive concept,those skilled in the art will appreciate that various modifications,additions and substitutions are possible without departing from thescope and spirit if the present general inventive concept as recitedherein an in the appended claims.

1. A method of forming characters for microprint, the method comprising:determining whether an initial font size of an image character is lessthan or equal to a predetermined size; determining whether an existingbitmap of the image character is stored for the character; rasterizing acharacter into a bitmap; skeletonizing the bitmap; reformatting thebitmap to maintain a character legibility by determining a rank of pixelsignificance of combined groups of pixels to be high, medium or low andselecting and deleting at least one combined group of less significantpixels than another combined group in the vertical or horizontaldirection; and forming halftoning cells from the reformatted bitmap. 2.The method of claim 1, wherein skeletonizing the bitmap is performed byparallel thinning.
 3. The method of claim 1, wherein reformatting thebitmap further comprises: determining a pixel significance of othercombined groups of pixels; and selecting and deleting, at a plurality ofstages of a multiple iteration reduction, other combined groups of lesssignificant pixels in the vertical or horizontal directions.
 4. Themethod of claim 3, wherein the selecting and deleting of the group ofless significant pixels applies a dynamic programming algorithm thatminimizes a cumulative cost of a trajectory using a graph at a regularnetwork according to a cost map.
 5. The method of claim 4, wherein apixel significance is determined using a weighted cost function, whereinwhite pixels of a background of the bitmap have a least cost, terminalor branch pixels of the skeleton have a high or a highest cost dependingon the distance to each of them from a reference point, and other pixelsof the skeleton of the image character have medium cost depending on thedistance to the nearest one of the terminal or branch pixels.
 6. Themethod of claim 1, wherein the halftoning cell is formed from one orseveral reformatted bitmaps.
 7. The method of claim 1, wherein thehalftoning cell is formed from a fragment of the reformatted bitmap. 8.An image forming apparatus comprising: an image processing unit to formcharacters for microprint by rasterizing a character into a bitmapskeletonizing the bitmap, reformatting the bitmap maintaining acharacter legibility by determining a pixel significance of combinedgroups of pixels to be ranked as high, medium or low and selecting anddeleting at least one combined group of less significant pixels thananother combined group in the vertical or horizontal direction, andforming halftoning cells from the reformatted bitmap; a storing unit tostore the reformatted bitmap; and a printing unit to print thecharacters for microprint on a print medium.
 9. The image formingapparatus of claim 8, wherein the image processing unit performsparallel thinning to skeletonize the bitmap.
 10. The image formingapparatus of claim 8, wherein the image processing unit furtherreformats the bitmap by determining a pixel significance of othercombined groups of pixels, and selecting and deleting, at a plurality ofstages of a multiple iteration reduction, other combined groups of lesssignificant pixels in the vertical or horizontal directions.
 11. Theimage forming apparatus of claim 10, wherein the image processing unitapplies a dynamic programming algorithm that minimizes a cumulative costof a trajectory using a graph at a regular network according to a costmap.
 12. The image forming apparatus of claim 11, wherein the imageprocessing unit determines the pixel significance using a cost function,wherein white pixels of a background of the bitmap have a least cost,terminal or branch pixels of the skeleton have a high or a highest costdepending on the distance to each of them from a reference point, andother pixels of the skeleton of the image character have medium costdepending on the distance to the nearest one of the terminal or branchpixels.
 13. The image forming apparatus of claim 8, wherein the imageprocessing unit forms the halftoning cell from one or severalreformatted bitmaps.
 14. The image forming apparatus of claim 8, whereinthe image processing unit forms the halftoning cell from a fragment ofthe reformatted bitmap.
 15. A method of forming characters formicroprint, the method comprising: determining that a font size of animage character is less than or equal to a predetermined size;determining that an existing bitmap of the image character has not beenstore for the character; performing a multiple iterative reduction ofthe image character to form a bitmap of the image character; anddetermining at stages of the multiple iterative reduction a ranked pixelsignificance from combined groups of pixels of the bitmap having a high,medium or low significance, and deleting combined groups of pixelshaving a small significance in a vertical or horizontal direction inrelation to the other combined groups of pixels.
 16. The method of claim15, comprising: deleting at least one combined group of characters toobtain a new copy of the bitmap having a changed size.
 17. The method ofclaim 1, wherein a font size for the rasterization is selected of 5 to 8typographical points.
 18. The method of claim 1, wherein thepredetermined size is one typographical point.
 19. The method of claim15, wherein the predetermined size is one typographical point.